210 Report of the Botanical Department of the 



when blight is destructive spraying will check the blight and 

 considerably increase the yield ; but the majority of potato grow- 

 ers have doubted that spraying is profitable on the average. 

 They argue that blight does not appear every year. In some 

 seasons it causes but little if any damage, yet the spraying must 

 be done regularly because it is impossible to foretell the appear- 

 ance of blight. The result is that in some seasons spraying is 

 profitable while in others it is unprofitable and growers doubt that 

 the aggregate gain will repay the expense of spraying for a 

 series of years. 



The Station set out to find an answer to the above question. 

 The investigation was begun in 1902 and concluded in 1911. 

 During ten consecutive years several potato spraying experiments 

 have been made each year. These experiments are of three 

 kinds: (1) Station ten-year experiments (two each year), car- 

 ried out entirely by the Station; (2) farmers' business experi- 

 ments (12 to 15 each year), conducted by farmers in cooperation 

 with the Station; (3) farmers' volunteer experiments carried 

 out entirely by farmers. This bulletin gives details of the experi- 

 ments made in 1911 and a summary of the results obtained in 

 the previous nine years. 



Bulletins of this series previously published are: 



No. 221. Potato Spraying Experiments 



'No. 241. Potato Spraying Experiments 



No. 264. Potato Spraying Experiments 



No. 279. Potato Spraying Experiments 



No. 290. Potato Spraying Experiments 



No. 307. Potato Spraying Experiments 



No. 311. Potato Spraying Experiments 



No. 323. Potato Spraying Experiments 



No. 338. Potato Spraying Experiments 



